将字段更改为属性

打破:API

受影响语言:Visual Basic和c# *

当你在visual basic中将一个普通的字段或变量更改为属性时，以任何方式引用该成员的任何外部代码都需要重新编译。

更改前的API:

Public Class Foo    
    Public Shared Bar As String = ""    
End Class

API变更后:

Public Class Foo
    Private Shared _Bar As String = ""
    Public Shared Property Bar As String
        Get
            Return _Bar
        End Get
        Set(value As String)
            _Bar = value
        End Set
    End Property
End Class    

示例客户端代码，可以工作，但随后被破坏:

Foo.Bar = "foobar"

Visual Studio扩展NDepend在API Breaking Changes类别中提供了几个规则来检测二进制级别的中断。只有定义了NDepend基线，这些规则才会执行。

API Breaking Changes: Types: This rule warns if a type publicly visible in the baseline, is not publicly visible anymore or if it has been removed. Clients code using such type will be broken. API Breaking Changes: Methods: This rule warns if a method publicly visible in the baseline, is not publicly visible anymore or if it has been removed. Clients code using such method will be broken. Note that if a method signature gets changed the old method version is seen as removed and the new method version is seen as added, so a breaking change will be detected on the old method version. API Breaking Changes: Fields: This rule warns if a field publicly visible in the baseline, is not publicly visible anymore or if it has been removed. Clients code using such field will be broken. API Breaking Changes: Interfaces and Abstract Classes: This rule warns if a publicly visible interface or abstract class has been changed and contains new abstract methods or if some abstract methods have been removed. Clients code that implement such interface or derive from such abstract class will be broken. Broken serializable types: This rule warns about breaking changes in types tagged with SerializableAttribute. To do so, this rule searches for serializable type with serializable instance fields added or removed since the baseline. Notice that it doesn't take account of fields tagged with NonSerializedAttribute. Avoid changing enumerations Flags status: This rule matches enumeration types that used to be tagged with FlagsAttribute in the baseline, and not anymore. It also matches the opposite, enumeration types that are now tagged with FlagsAttribute, and were not tagged in the baseline. Being tagged with FlagsAttribute is a strong property for an enumeration. Not so much in terms of behavior (only the enum.ToString() method behavior changes when an enumeration is tagged with FlagsAttribute) but in terms of meaning: is the enumeration a range of values or a range of flags?

还有3个代码查询建议让用户浏览新的公共API元素:

新的公开可见类型。 新的公开可见方法。 新的公开可见字段。

将隐式接口实现转换为显式接口实现。

打破:源和二进制

受影响语言:所有

这实际上只是改变方法的可访问性的一种变体——它只是更微妙一点，因为很容易忽略一个事实，即并非所有对接口方法的访问都必须通过对接口类型的引用。

更改前的API:

public class Foo : IEnumerable
{
    public IEnumerator GetEnumerator();
}

API变更后:

public class Foo : IEnumerable
{
    IEnumerator IEnumerable.GetEnumerator();
}

样例客户端代码在更改前工作，更改后被破坏:

new Foo().GetEnumerator(); // fails because GetEnumerator() is no longer public

具有可空类型参数的重载方法

类型:源级中断

受影响的语言:c#， VB

更改前的API:

public class Foo
{
    public void Bar(string param);
}

更改后的API:

public class Foo
{
    public void Bar(string param);
    public void Bar(int? param);
}

样例客户端代码在更改前工作，更改后失效:

new Foo().Bar(null);

例外:以下方法或属性之间的调用是模糊的。

添加具有默认值的参数。

中断类型:二进制级别的中断

即使调用源代码不需要更改，它仍然需要重新编译(就像添加常规参数一样)。

这是因为c#将参数的默认值直接编译到调用程序集中。这意味着如果您不重新编译，您将得到一个MissingMethodException，因为旧程序集试图调用带有较少参数的方法。

更改前的API

public void Foo(int a) { }

更改后的API

public void Foo(int a, string b = null) { }

之后被破坏的示例客户端代码

Foo(5);

客户端代码需要在字节码级别上重新编译为Foo(5, null)。被调用的程序集将只包含Foo(int, string)，而不是Foo(int)。这是因为默认参数值纯粹是一种语言特性，. net运行时对它们一无所知。(这也解释了为什么在c#中默认值必须是编译时常量)。

重命名接口

休息一下:源代码和二进制文件

受影响的语言:很可能全部，用c#测试。

更改前的API:

public interface IFoo
{
    void Test();
}

public class Bar
{
    IFoo GetFoo() { return new Foo(); }
}

API变更后:

public interface IFooNew // Of the exact same definition as the (old) IFoo
{
    void Test();
}

public class Bar
{
    IFooNew GetFoo() { return new Foo(); }
}

示例客户端代码，可以工作，但随后被破坏:

new Bar().GetFoo().Test(); // Binary only break
IFoo foo = new Bar().GetFoo(); // Source and binary break